Content Cruising System : Peer-to-Peer Distribution System for Location-based Contents

1. Content Cruising System :Peer-to-Peer Distribution System for Location-based Contents Takaaki Ishida (ishi@sfc.wide.ad.jp) Keijiro Ehara(popo@sfc.wide.ad.jp) Masayoshi Imaike(isle@sfc.wide.ad.jp) Graduate School of Media and Governance of Keio University JAPAN

2. Background1:Location-based Service The service distributing contents to users depending on their positional information is called location based service. “ROAD CONSTRUCTION, NEXT 4 MILES” “You can find a McDonald's around here!” Source of image: KDDI Corporation JAPAN

3. Current Operation of Location-based Service • It requires: • Costly equipments (numerous base stations, Content storage/distribution servers, etc.) • Central management. • Continuous network connectivity . • The problem of single point of failure arises • We cannot use it: • in some developing region without such an infrastructure • in a disastrous situation where the infrastructure is damaged Internet GPS Base station Data Base Send Location information as a query areaA Get it’s Location information Retrieve content of it’s area from DB area A

4. Research Motivation It is required to realize free and robust location based services that do not necessarily depend on specific infrastructures. We designed new location-based contents sharing system by using of wireless P2P ad-hoc communication instead of current central management model. →Content Cruising System

5. Background2: Ad-hoc communication In the mobile wireless Communication: Mobile nodes have their radio device’s range.(ex. Bluetooth → 10m, IEEE802.11b →100m, etc.) In their radio range, they can: • detect the nodes which are close geographically • broadcast contents to their One-hop neighbors which they happen to meet. • The nodes which receive the content forward it to other nodes. Wireless P2PAd-hoc communication

6. Merits and Demerits Using the catenation of ad-hoc communication as a location based services generates both merits and demerits. Merits: • Contents are transferred to further areas by physical movements of numerous mobile nodes. • Costly equipments and network infrastructure are not needed. Demerits: • Contents are spread disorderly in wide area through multi-hop communication.

7. Our Approach Location-based service will be realized If information flooding can be suppressed to fixed geographical areas. To attain the goal which mentioned above: • Each content shall have it’s “Geographical destination” and “Duration” previously. • Content sender adds these information to each content as meta-data. • Mobile nodes which receive the content change frequency of transmitting the content depending on their location information which is obtained by GPS. →Contents are gathered around destination area autonomously by cooperation of mobile nodes.

8. Content Cruising System

9. Objectives • Location based transmission: Contents are transferred and sustained in a specified area autonomously. • Location-awareness: Contents are found by users in a relevant location automatically. • Location based selection: Unnecessary contents are eliminated based on the user's location.

10. Overview Receivers & Mediators prompt the content to be transferred to the destination point, .and to be remained around the destination area during the duration by cooperation of scattered mobile nodes. Sender: 1) adds the metadata which describes “Destination point”, “Duration”, and “Content ID” to the content. 2) then send it to one-hop neighbors which happen to meet. Content Cruising System metadata Content

11. Framework of Servant Application CCS is operated by cooperation of simple servant applications which have same function installed on each mobile nodes. Servant application consists of 4 modules: • Sender Module • Receiver Module • Storage Module • Context /Status Manager

12. Receive Contents Send Contents Contents Monitoring Contents Contents Controlling Other Mobile Nodes (One-hop neighbors) Sender module broadcasts the content according to the Transmission Algorithm Receiver Sender Context Sensing Equipments( GPS, Clock, etc ) Other Programs( To Display or Play Contents ) Context/Status Manager Storage module compares the Content ID of the new content with those of the old ones in order to detect the duplication. If duplication is detected, this module discards the old content . Storage Servant Application Inside of Mobile Node

13. Configuration of Transmission Algorithm “d” is the distance from the destination point, “a” is a coefficient, . ”k” is the parameter which define the dependence with distance. Centripetal Force Interval Time of Sending a 2a 1 -kd a y = ae y -1 =a -１ e kｄ 2 a R R (0.0) (0.0)

14. Demonstration

15. Around this area , you’ll find green message Screen of real node Screen of projector Both of real and virtual nodes distribute messages according to their location（transmitting algorithm of the centripetal force） A screen image of the CCS demonstration Virtual Simulation （Demo2：Generating virtual nodes, and realization of assuming environment in virtual space） Mapping situation Red balls are real, Blue balls are virtual nodes. 802.11b Real Space Communication （Demo1：ad-hoc Communication using radio-device ＆ IPv6） 38 37 36 35 137 138 142 latitude 139 140 141 143 longitude

16. Summary • The purpose of our research is to realize the contents distribution system which is decentralized in form that mobile nodes distributed in various places sharing the functions to store and to distribute the contents. • We proposed the Content Cruising System to realize the form of a decentralized content-transmission system in real space. • This system brings about the mechanism in which contents are transmitted autonomously, by adopting a simple algorithm in ad-hoc communication. • Estimated effectiveness of the transmission algorithm which is applied in CCS is verified by the simulation with assumed movement patterns of people in real space.

17. Thank you.

19. Demonstration 1 • Objectives: • To confirm our designed system is work well through the implementation of servant programs on • Outline： • Users get their location information by GPS. • Users send content depending on transmission algorithm to their one-hop neighbors by IPv6 link-local multicast.

20. Architecture of Demonstration1 PDA a PDA b Presentation GPS GPS Presentation PresentationAlgorithm PresentationAlgorithm TransmissionAlgorithm SelectionAlgorithm Receive Timer Algorithm Send ContextManager ContextManager IPv6Link-local multicast IPv6Link-local multicast Storage Storage TransmissionAlgorithm Timer Algorithm SelectionAlgorithm Send Receive

21. About each Algorithm • Transmission Algorithm： • Objectives:To change the frequency of transmission depending on the relation between their location and content’s destination. • Selection Algorithm： • Objectives:To avoid the depuration of content which it received. • Operation:It compares the Content ID of the new content with those of the old ones in order to detect the duplication.If duplication is detected, this module discards the old content . • Timer Algorithm: • Objectives:To set the timer to next transmission on each content depending on Transmission Algorithm. • Operation: • Set the timer to next transmission on each content • Reset a timer of the content when it received same content from others. • Stop resetting a timer randomly. • Presentation Algorithm： • Objectives:To pick up the content whose destination is close to user’s location from Storage Module. • Operation:Display the content whose destination is within the range of 5 meters.

22. Demonstration 2 • Objectives: • To introduce the overview of CCS which is completed by autonomous cooperation of many nodes through working with a simulator that represent people’s move. • Operation: • Simulator Generates numerous “Virtual nodes” as an emulator which has same function of CCS servant application. • “Real nodes(=PDA)” are sending their location information which is gotten by GPS to a simulator, and they work as if one of the virtual nodes on the simulator. • Each real node’s status which is calculated on a simulator is send back to real node, and it is shown on the display of each PDA.

23. Architecture of Demonstration2 Simulator Emulator of PDA a Emulator of PDA b Emulator of PDA c Emulator of Virtual Node Storage Storage Storage Storage Context Manager Context Manager Context Manager Context Manager PresentationAlgorithm TransmissionAlgorithm PresentationAlgorithm TransmissionAlgorithm PresentationAlgorithm TransmissionAlgorithm PresentationAlgorithm TransmissionAlgorithm SelectionAlgorithm SelectionAlgorithm SelectionAlgorithm SelectionAlgorithm Receive Send Receive Send Receive Send Receive Send Walking Model on SimulatororCursor Key of Remote Host Calculated by Simulator Connected by WLAN（IPv6 or IPv4 Network） PDA a PDA b PDA c Presentation Presentation Presentation ContextManager ContextManager ContextManager GPS GPS GPS

24. Mapモードの動作イメージ • 前提： • コンテンツのヘッダは、下記のデータが含まれている。 • ContentID（位置情報＋発信時刻＋IPアドレスをMD5,SHA-1でハッシュ化したもの） • Destination（コンテンツの目的地） • Duration（コンテンツの生存時間） • IPアドレス（発信したノードのSourceアドレス） • 発信者の位置情報 • 画面説明： • 地図中の円は、PDAのラジオレンジであり、この円が自分の現在地を中心（赤丸）に地図上をスクロールする。 • 届いたコンテンツのDestinationは×印で地図上にplotされる。受信時は点滅（または赤色）する。 • 地図上にplotされたDestinationはDuration（生存時間）が過ぎると消滅する。 • コンテンツを送信したノードは”5”を元に、一定時間緑の■で地図上にplotされる。 • 自分が送信するときは、赤丸が点滅する。 • 受け取ったコンテンツのうち、Destinationが半径5m以内に入ったものは、Message Boardにコンテンツが表示される。（複数ある場合は最も近いもののみを表示） • “Write a Message”をクリックすると「メッセージ書き込みモード」に。”Debugging Mode”をクリックすると「デバッグモード」へと切り替わる。 Map mode （PDA a） Message Board You find a Message !“ROAD CONSTRUCTION, NEXT 4 MILES” Go to Message Writing Mode Debugging Mode

25. メッセージ書き込みモードの動作イメージ • 画面説明： • “Target Your Content’s Destination”： • 地図上で、カーソルキーを用いてコンテンツの目的地を定める。 • “Writing Message”： • メッセージを作成 • “Drop Your Content”： • コンテンツを発信する。 Massage Writing mode （PDA a） Target Your Content’s Destination Writing Message “Famous rest rant is around here !” Drop your Content Go to Message Writing Mode Debugging Mode

26. デバッグモードの動作イメージ • 目的： • CCSのアプリケーション動作を、コンテンツ送受信の流れで説明する。 • 画面説明： • 自分が受け取ったコンテンツと送信したコンテンツをそれぞれ時系列で上から順に表示する。（メッセージは上に新しいメッセージが積み上げられていく）。 • 表示するものは、 • メッセージの内容（赤字） • Source Address（from 以下） • Destination Address（=リンクローカル・ブロードキャストアドレス送信時のみ。To 以下） • 受信日時（at 以下） • を今のところ検討中。 Debugging mode （PDA a） Now you are receiving these Contents You received “Famous rest rant is around here !”from fe80::205:4eff:fe40:555bat Sat, 15 May 2004 16:08:09 +0900 (JST)------------------------------ You received “ROAD CONSTRUCTION, NEXT 4 MILES” from fe80::205:4eff:fe40:777bat Sat, 15 May 2004 16:07:55 +0900 (JST)------------------------------ You send “Watch your step !”to fe80::205:4eff:fe::0at Sat, 15 May 2004 16:07:50 +0900 (JST)------------------------------ Drop your Content Go to Message Writing Mode Debugging Mode

27. Issue of Using CCS under Sparse Movements of Nodes

28. Transmission Schedule • “Context Manager” has a timer to schedule the time for each content to be sent. • When receiving the same content from other nodes, “Storage module” discards the older one, and “Context Manager” will set it’s timer of the new content. → We call this workings “Timer-Reset” • In CCS, transmitting frequency becomes higher as a node approaches the destination (cf. transmission algorithm). • Hence, only the closest node to destination among its one-hop neighbors always sends the content to other nodes by this mechanism.

29. Working of “Timer-Reset” Destination of the content Each node resets its timer of this content to send Hidden terminal problem will be generated × We call the node like this “Glued Node”

30. Approach to solve “Glued node’s problem” There thought to be 2 ways to avoid this problem. • Passive avoidance • Waiting the nodes’ movements • Active avoidance • Adoption of random timer-reset

31. B C A C A B C B A C A 1.Solved by nodes’ movement Star-mark : content’s destination point Node A: First content’s holder When NodeA approaches NodeB and sends the content to NodeB, Node C will be “Glued Node”. • When the glued node’s problem occurs: • The situations the glued node will be able to receive the content are shown below. B B 3: B approaches destination point closer than A 1: B is separated from A 2: A communicates with C directly.

32. 2.Solved by adoption of “Random Timer-Resets” • By adding a redundancy to normal “Timer-Reset”, to make content be sent to Glued nodes. • In precise, we cause ‘no-reset event’ to “Timer-Reset” by a certain probability,and when the “no-reset event” occurs, the nodes which received same content : • does not reset their timer. • Send the content to their one-hop neighbors immediately. • We call this working “Random Timer-Resets”.

33. Working of “Random Timer-Resets” Destination of the content “no-reset event” occurs The node send content to one-hop neighbors Irrespective of the remaining time Glued Node

34. Types of Location-based Service Type2:Retreive location-based contents by using of GPS Type1:Cell Broadcast of many radio station Internet station A GPS Data Base Location information area A station B station C However, they must require: Wide area wireless-network, Costly equipments, and Central management. Moreover, the problem of single point of failure arises

35. Background1: Location based service Geographically dependent contents: Traffic information, Campaigns advertisements of local stores, Evacuation instructions for a local disaster, etc. The value of this kind of contents depends on Time and Place These Contents’ Value becomes: • higher around destination area • lower as time go on. for both senders and receivers The service distributing contents to users at appropriate time and place is generally called location based service. Content’s value in Real Space Content’s destination point

36. Geographical destination of each content is set previously. • The node which receives the content calculates its distance from the destination. • As a node move closer to destination, the node tends to send the content. • Informational flood suppressed to fixed targeted area. • And the node that newly enters into the area will receive the content

37. What is Content Cruising System? But, before that, I will talk about our motivation of this research.

38. Research Motivation 目的： 災害時などに備え、インターネットへの接続や We use Wireless P2P ad-hoc communication as free and robust location based services instead of current central management model. Merit: • Contents are transferred to further target areas by physical movements of numerous mobile nodes. • Costly equipments and network infrastructure are not needed. Problem: →Free and robust location based services are realized by co-operation of scattered mobile nodes.

39. Analogy of Voice Communication

40. Problems Through the catenation of ad-hoc communication, contents are spread to wide area by physical movements of mobile nodes without specific infrastructure or equipments. →This propagation model is similar to the rumors flooding model. Contents are spread disorderly in wide area through multi-hop communication.